mysql中select和where子句优化的总结

SELECT COUNT(*) FROM tbl_name;

SELECT MIN(key_part1),MAX(key_part1) FROM tbl_name;

SELECT MAX(key_part2) FROM tbl_name

  WHERE key_part1=constant;

SELECT ... FROM tbl_name

  ORDER BY key_part1,key_part2,... LIMIT 10;

SELECT ... FROM tbl_name

  ORDER BY key_part1 DESC, key_part2 DESC, ... LIMIT 10;

SELECT key_part1,key_part2 FROM tbl_name WHERE key_part1=val;

SELECT COUNT(*) FROM tbl_name

  WHERE key_part1=val1 AND key_part2=val2;

  SELECT key_part2 FROM tbl_name GROUP BY key_part1;

SELECT ... FROM tbl_name

  ORDER BY key_part1,key_part2,... ;

SELECT ... FROM tbl_name

   ORDER BY key_part1 DESC, key_part2 DESC, ... ;